The present invention relates to an aluminum electrolytic capacitor utilized in various electronic apparatuses.
A conventional type of aluminum electrolytic capacitor has the following structure as shown in FIG. 2: A capacitor element 1 is housed in a metal case 2 made of aluminum and shaped in cylinder with a bottom plate, and an opening of the metal case 2 is sealed by a sealer 3 in order to prevent driving electrolyte from vaporizing. Further, an outside of the metal case 2 is covered by a tube 4 made of resin. The capacitor element 1 comprises a rolled member of an anode foil and a cathode foil as well as a separator therebetween, and driving electrolyte impregnated into the rolled member, where the anode foil employs a metal foil (used for valve action) of which surface is roughened, and a dielectric oxide film is formed on the surface, and the cathode foil employs an aluminum foil of which surface is roughened.
However, because the metal case 2 of the above aluminum electrolytic capacitor is made of only aluminum, the case 2 is vulnerable to being deformed resulting from pressure rising within the case 2 when the capacitor is left in a high temperature atmosphere, and in due course of time, an explosion-proof valve 5 formed by a thin-part of the bottom plate is activated, thereby the capacitor loses its original function.